Cathode circulation system of fuel cell and its control method

ABSTRACT

Some embodiments of the disclosure provide a cathode circulation system of a fuel cell connected to a power generation unit of the fuel cell. The cathode circulation system includes a first gas supply tank for providing an inert gas, a second gas supply tank for providing a reaction gas, a mixing tank connected to the first gas supply tank and the second gas supply tank for mixing the inert gas and the reaction gas, a gas-liquid separator connected to the power generation unit, and at least one cathode gas pump provided between the mixing tank and the gas-liquid separator and between the mixing tank and the power generation unit.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. provisional application No. 63/310,151, filed on Feb. 15, 2022, the disclosure of which is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

The disclosure relates generally to the field of cathode circulation systems and their control methods for fuel cells. More specifically, the disclosure relates to cathode circulation systems and their control methods which allow conventional fuel cells to directly input pure oxygen.

BACKGROUND

A fuel cell is a device that directly converts the chemical energy of fuel into electrical energy, also known as electrochemical generator. In the history of energy development, fuel cells are the fourth type of power generation technology following hydroelectric power, thermal power, and atomic power.

Compared with hydroelectric power and thermal power, fuel cells are a highly efficient and clean power source. Conventional fuel cells use substances such as alcohol, natural gas, and hydrogen as fuel, and directly convert them into electrical energy through oxidation-reduction reactions. Its high energy conversion rate and relatively low environmental pollution make it the most environmentally friendly sustainable power generation method currently available. For example, a hydrogen fuel cell uses hydrogen and oxygen from the air as fuel and oxidant, and only produces water as a by-product. Hydrogen fuel cells typically use a proton exchange membrane (PEM) as the barrier between the anode and cathode, and are therefore called PEM fuel cells.

In practical fuel cell applications, in the air-filled atmosphere, the proton exchange membrane and catalyst used in conventional proton exchange membrane fuel cells are designed with a thin film thickness and catalyst amount sufficient to allow the oxygen in the air to react with the fuel gas (hydrogen) of the fuel cell. However, if fuel cells are applied in environments such as outer space or deep sea where air is not easily obtained, a pure oxygen fuel cell is an option for these environments. However, if the conventional air fuel cell is used in a pure oxygen fuel cell system with a direct input of high-content oxygen, the high redox reaction is likely to occur in an environment with insufficient proton exchange membrane thickness and catalyst content, which easily reduces the efficiency and lifespan of the thin film and catalyst. Of course, this directly affects the performance and lifespan of the fuel cell.

However, increasing the thickness of the PEM and the amount of catalyst may allow the PEM to withstand higher levels of redox reactions, but it may also reduce the efficiency of proton transport and increase the difficulty in preparing the film. In addition, since the most effective catalyst in prior art is usually based on palladium, increasing the amount of catalyst will inevitably significantly increase the overall production cost of the fuel cell. In terms of safety considerations, the input of pure oxygen is prone to combustion reactions due to microleaks, making the use of pure oxygen fuel cells a significant concern.

SUMMARY

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify critical elements or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented elsewhere.

In some embodiments, the disclosure provides a cathode circulation system of a fuel cell connected to a power generation unit of the fuel cell. The cathode circulation system includes a first gas supply tank for providing an inert gas, a second gas supply tank for providing a reaction gas, a mixing tank connected to the first gas supply tank and the second gas supply tank for mixing the inert gas and the reaction gas, a gas-liquid separator connected to the power generation unit, and at least one cathode gas pump provided between the mixing tank and the gas-liquid separator and between the mixing tank and the power generation unit.

Optionally, a humidifier is provided between the mixing tank and the power generation unit.

Optionally, a buffer tank is provided between the gas-liquid separator and the mixing tank.

Optionally, a first flow meter is provided between the first gas supply tank and the mixing tank, and a second flow meter is provided between the second gas supply tank and the mixing tank.

Optionally, each one of the first flow meter and the second flow meter operates individually or simultaneously based on at least one of a concentration gradient and a pressure gradient of at least one of the inert gas and the reaction gas in the cathode circulation system.

Optionally, the at least one cathode gas pump provides a gain value based on an operation of at least one of the first flow meter and the second flow meter.

Optionally, the at least one cathode gas pump is provided between the mixing tank and a buffer tank; and a valve or a pump is provided between the mixing tank and a humidifier, which may be same or different from the at least one cathode gas pump.

Optionally, a reaction gas concentration meter is provided between the mixing tank and the power generation unit, and the reaction gas concentration meter is set with a system operation concentration threshold.

Optionally, a temporary water tank is provided between the gas-liquid separator and a buffer tank.

Optionally, a mixing ratio of the reaction gas and the inert gas is substantially similar to that of oxygen and nitrogen in air.

In other embodiments, the disclosure provides a method for controlling the cathode circulation system. The method includes following steps: providing the inert gas to the cathode circulation system, providing the reaction gas to the cathode circulation system when a pressure value of the inert gas in the mixing tank is not greater than 80% of an operating pressure value, delivering mixture of the inert gas and the reaction gas to the power generation unit for redox reactions until the pressure value in the mixing tank reaches the operating pressure value, and detecting at least one of an output current of the power generation unit and a concentration of the reaction gas and adjusting a flow rate of at least one of the inert gas and the reaction gas.

Optionally, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is less than a corresponding threshold value, further increasing a supply of the reaction gas and selectively adjusting a supply of the inert gas, wherein a threshold value for the output current corresponds to a current value and another threshold value for the concentration of the reaction gas corresponds to a concentration value.

Optionally, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is less than the corresponding threshold value and a total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing the supply of the reaction gas, and as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value but the total pressure in the cathode circulation system is still less than the set cathode gas pressure, further increasing the supply of the inert gas until the total pressure in the cathode circulation system is equal to the set cathode gas pressure.

Optionally, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is less than the corresponding threshold value and a total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing the supply of the reaction gas, and as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value and the total pressure in the cathode circulation system is equal to the set cathode gas pressure, further making no adjustment for the inert gas.

Optionally, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to a corresponding threshold value and a total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing a supply of the inert gas but making no adjustment for the reaction gas, and stopping supplying the inert gas until the total pressure in the cathode circulation system is equal to the set cathode gas pressure, wherein the threshold value for the output current corresponds to a current value and the threshold value for the concentration of the reaction gas corresponds to a concentration value.

Optionally, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is larger than a corresponding threshold value, further reducing a supply of the reaction gas until at least one of the output current and the concentration of the reaction gas is equal to the corresponding threshold value, and a total pressure in the cathode circulation system is equal to a set cathode gas pressure, wherein the threshold value for the output current corresponds to a current value and the threshold value for the concentration of the reaction gas corresponds to a concentration value.

Optionally, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is larger than the corresponding threshold value, further reducing a supply of the reaction gas, and further reducing the supply of the inert gas until as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value, but the total pressure in the cathode circulation system is larger than the set cathode gas pressure.

Optionally, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is larger than the corresponding threshold value, further reducing a supply of the reaction gas, and further increasing the supply of the inert gas until at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value, but the total pressure in the cathode circulation system is less than the set cathode gas pressure.

Optionally, further comprising changing a gain of the cathode gas pump for adjusting when adjusting the flow rate of at least one of the inert gas and the reaction gas.

In further embodiments of the disclosure, the cathode circulation system comprises at least two gas supply tanks, a mixing tank, a gas-liquid separator and at least one cathode gas pump. Each of the gas supply tanks provides an inert gas and a reaction gas, respectively. The mixing tank is connected to the gas supply tanks and mixing the inert gas and the reaction gas. The gas-liquid separator is connected to the power generation unit. The cathode gas pump is connected to at least one location between the mixing tank and the gas-liquid separator and between the mixing tank and the power generation unit.

An embodiment of the disclosure discloses that a humidifier is further provided between the mixing tank and the power generation unit to balance the humidity of the cathode inlet of the fuel cell.

An embodiment of the disclosure discloses that a flow meter is respectively provided between each supply gas tank and the mixing tank.

An embodiment of the disclosure discloses that a flow meter is respectively provided between each supply gas tank and the mixing tank.

An embodiment of the disclosure discloses that each of the flow meter operates individually or simultaneously based on at least one concentration gradient or pressure gradient of the inert gas and the reaction gas occurring in the cathode circulation system.

An embodiment of the disclosure discloses that the cathode gas pump provides a gain value based on operation of each of the flow meter.

An embodiment of the disclosure discloses that the cathode gas pump is connected between the mixing tank and the buffer tank, and a valve or a pump is provided between the mixing tank and the humidifier, which may be the same or different from the cathode gas pump.

Meanwhile, a control method is also disclosed in the disclosure. The method comprises the following steps. First, providing the inert gas to the cathode circulation system. Then, when the pressure value of the inert gas in the mixing tank is not greater than 80% of an operating pressure value, providing the reaction gas to the cathode circulation system. Then, until the pressure value in the mixing tank reaching the operating pressure value, delivering mixture of the inert gas and the reaction gas to the power generation unit for redox reactions. Finally, detecting at least one of an output current of the power generation unit and a concentration of the reaction gas, and adjusting flow rate of at least one of the inert gas and the reaction gas.

An embodiment of the disclosure discloses that detecting at least one of output current or concentration of the reaction gas in the fuel cell and at least one of the detected output current or concentration of the reaction gas is less than a corresponding threshold value, and further increasing a supply of the reaction gas and selectively adjusting a supply of the inert gas, the threshold value for the output current corresponds to a current value, and the threshold value for the concentration of the reaction gas corresponds to a concentration value.

An embodiment of the disclosure discloses that detecting at least one of output current or concentration of the reaction gas in the fuel cell and at least one of the detected output current or concentration of the reaction gas is less than the corresponding threshold value, and the total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing the supply of the reaction gas, and as at least one of the output current of the power generation unit and the concentration of the reaction gas detected by the power generation unit is equal to the corresponding threshold value but the total pressure in the cathode circulation system is still less than the set cathode gas pressure, further increasing the supply of the inert gas until the total pressure in the cathode circulation system equaled to the set cathode gas pressure is detected.

An embodiment of the disclosure discloses that detecting at least one of output current or concentration of the reaction gas in the fuel cell and at least one of the detected output current or concentration of the reaction gas is less than the corresponding threshold value, and the total pressure in the cathode circulation system is less than the set cathode gas pressure, further increasing the supply of the reaction gas, and as at least one of the output current of the power generation unit and the concentration of the reaction gas detected by the power generation unit is equal to the corresponding threshold value and the total pressure in the cathode circulation system is equal to the set cathode gas pressure, further doing no adjustments for the inert gas.

An embodiment of the disclosure discloses that detecting at least one of output current or concentration of the reaction gas in the fuel cell and at least one of the detected output current or concentration of the reaction gas is equal to a corresponding threshold value, and a total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing a supply of the inert gas but doing no adjustments for the reaction gas, and stopping supplying the inert gas until the total pressure in the cathode circulation system equaled to the set cathode gas pressure is detected, the threshold value for the output current corresponds to a current value, and the threshold value for the concentration of the reaction gas corresponds to a concentration value.

An embodiment of the disclosure discloses that detecting at least one of output current or concentration of the reaction gas in the fuel cell and at least one of the detected output current or concentration of the reaction gas is larger than a corresponding threshold value, further reducing a supply of the reaction gas until at least one of the detected output current or concentration of the reaction gas is equal to the corresponding threshold value, and the total pressure in the cathode circulation system equaled to the set cathode gas pressure is detected, the threshold value for the output current corresponds to a current value, and the threshold value for the concentration of the reaction gas corresponds to a concentration value.

An embodiment of the disclosure discloses that detecting at least one of output current or concentration of the reaction gas in the fuel cell and at least one of the detected output current or concentration of the reaction gas is larger than the corresponding threshold value, further reducing a supply of the reaction gas, and further reducing the supply of the inert gas until at least one of the detected output current or concentration of the reaction gas is equal to the corresponding threshold value, but the total pressure in the cathode circulation system larger than the set cathode gas pressure is detected.

An embodiment of the disclosure discloses that detecting at least one of output current or concentration of the reaction gas in the fuel cell and at least one of the detected output current or concentration of the reaction gas is larger than the corresponding threshold value, further reducing a supply of the reaction gas, and further increasing the supply of the inert gas until at least one of the detected output current or concentration of the reaction gas is equal to the corresponding threshold value, but the total pressure in the cathode circulation system less than the set cathode gas pressure is detected.

An embodiment of the disclosure discloses that in the step of adjusting flow rate of at least one of the inert gas and the reaction gas, changing the gain of the cathode gas pump for adjusting.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present disclosure are described in detail below with reference to the attached drawing figures.

FIG. 1A shows a block diagram of the cathode circulation system of the fuel cell according to an embodiment of the disclosure.

FIG. 1B shows a flowchart of the control method of the cathode circulation system of the fuel cell as shown in FIG. 1A.

FIG. 2A shows a block diagram of the cathode circulation system of the fuel cell according to another embodiment of the disclosure.

FIG. 2B is shows flowchart of the control method of the cathode circulation system of the fuel cell as shown in FIG. 2A.

DETAILED DESCRIPTION

The following describes some non-limiting exemplary embodiments of the invention with reference to the accompanying drawings. The described embodiments are merely a part rather than all of the embodiments of the invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the disclosure shall fall within the scope of the disclosure.

The cathode circulation system 1 of the fuel cell disclosed in the disclosure is connected to the power generation unit 2 of the fuel cell. The cathode circulation system 1 of the fuel cell disclosed in the disclosure includes at least two gas supply tanks 11 a, 11 b, a mixing tank 12, a humidifier 13, a gas-liquid separator 14, a buffer tank 15, and at least one cathode gas pump 16. Each of the gas supply tanks 11 a, 11 b supplies an inert gas and a reaction gas respectively. The mixing tank 12 is connected to the gas supply tanks 11 a, 11 b and is used to mix the inert gas and the reaction gas. The humidifier 13 is connected between the mixing tank 12 and the power generation unit 2. The gas-liquid separator 14 is connected to the power generation unit 2. The buffer tank 15 is connected between the gas-liquid separator 14 and the mixing tank 12. At least one cathode gas pump 16 is connected to at least one of the mixing tank 12 and the buffer tank 15 and the humidifier 13. The gas supply tanks 11 a and 11 b supply the reaction gas: oxygen, and the inert gas: nitrogen. A flow meter 17 a, 17 b is provided at the gas outlet of each of the gas supply tanks 11 a, 11 b. The flow meters 17 a, 17 b will act separately or simultaneously depending on the concentration gradient and pressure gradient of oxygen and nitrogen in the cathode circulation system 1, but the concentration gradient is usually determined based on the output current of the power generation unit 2.

In this embodiment, the example is given of connecting the cathode gas pump 16 between the mixing tank 12 and the humidifier 13. The cathode gas pump 16 will provide a gain value based on the gas flow controlled by the flow meters 17 a, 17 b.

In addition, the gas-water separator 14 and buffer tank 15 of this embodiment are connected to a temporary water tank 3. The gas-water separator 14 may discharge water into the temporary water tank 3, and there is a return pipeline between the buffer tank 15 and the temporary water tank 3 to improve the efficiency of water drainage and gas recovery.

Continuing, the control method of the cathode circulation system 1 of the fuel cell shown in FIG. 1A is illustrated in FIG. 1B. In order to simulate an air environment and dynamically control the anode gas in real time, in the control method disclosed in this invention, first in step S01, nitrogen gas (an inert gas) is supplied to the cathode circulation system 1 from the supply tanks 11 a and 11 b. Subsequently, in step S02, when the pressure of nitrogen gas in the mixing tank 12 is not greater than 80% of the operating pressure, oxygen gas (reaction gas) is supplied to the cathode circulation system 1. Then, in step S03, oxygen gas is continuously supplied to the mixing tank 12 until the pressure value of the mixing tank 12 reaches the set operating pressure. After the nitrogen gas and oxygen gas are mixed and humidified by the humidifier 13, they are transported to the power generation unit 2 for the redox reaction. Finally, in step S04, the actual oxygen consumption is calculated based on the output current of the power generation unit 2, and the settings of flow meters 17 a and 17 b are adjusted accordingly. At the same time, the cathode gas pump 16 provides a gain value to adjust the oxygen and hydrogen flowing through the mixing tank 12, so that the mixed oxygen and hydrogen may be transported under controlled conditions before entering the power generation unit 2. Because the cathode gas pump 16 in this embodiment is directly installed on the gas supply pipeline of the power generation unit 2, the control of the delivery of oxygen and nitrogen to the power generation unit 2 has extremely high precision.

More specifically, when the detected output current of the power generation unit 2 is less than a threshold value, it indicates that the power generation efficiency of the power generation unit 2 is insufficient, that is, the degree of oxidation-reduction reaction inside it is insufficient, so it may be necessary to increase the supply of oxygen and selectively adjust the supply of nitrogen: one embodiment is to simultaneously increase the supply of oxygen and nitrogen, and the other embodiment is to only increase the supply of oxygen without adjusting the supply of nitrogen.

In the first pattern, when the output current of power generation unit 2 is lower than the threshold and the total pressure in cathode circulation system 1 is lower than the preset cathode gas pressure, in addition to increasing the supply of oxygen first to raise the output current of power generation unit 2 to the threshold, if the total gas pressure in cathode circulation system 1 still cannot be restored to the preset cathode gas pressure, it means that the non-reacting nitrogen gas may be leaking. Therefore, it may be necessary to increase the supply of nitrogen gas until the total pressure in cathode circulation system 2 is restored to the preset cathode gas pressure. In the other pattern, when the output current of power generation unit 2 is lower than the threshold and the total pressure in cathode circulation system 1 is lower than the preset cathode gas pressure, if it is found that after increasing the supply of oxygen to raise the output current of power generation unit 2 to the threshold, the total pressure in cathode circulation system 1 has also been restored to the preset cathode gas pressure, it means that there is no leakage of non-reacting nitrogen gas, so there is no need to adjust the supply of nitrogen gas.

In addition, when there is no deficiency or leakage of oxygen, the output current of the detected power generation unit 2 will be equal to the threshold value because the power generation efficiency of the power generation unit 2 is normal and the internal redox reaction is complete. However, if the total pressure in the cathode circulation system 2 is less than the preset cathode gas pressure, it indicates that nitrogen may be leaking, so it may be necessary to increase the nitrogen supply. However, in this case, there is no need to adjust the oxygen supply. Finally, when the total pressure in the cathode circulation system 2 returns to the preset cathode gas pressure, the increase in nitrogen supply may be stopped.

In the case of excess oxygen supply, since the power output of the power generation unit 2 exceeds the demand and excessive oxidation-reduction reactions occur internally, the detected output current of the power generation unit 2 will be greater than the threshold value. Therefore, it may be necessary to first reduce the supply of oxygen and selectively adjust the supply of nitrogen: one pattern is to increase the supply of nitrogen, another pattern is to not adjust the supply of nitrogen, and another pattern is to reduce the supply of nitrogen.

In the first pattern, when it is detected that the output current of the power generation unit 2 is greater than the threshold value, indicating that the oxygen supply in the power generation unit 2 is excessive, the oxygen supply must be reduced first until the output current of the power generation unit 2 may be restored to the threshold value. Moreover, the total pressure in the cathode circulation system 1 gradually returns to the preset cathode gas pressure due to the increased oxygen supply. This indicates that there is no nitrogen leakage, and therefore, there is no need to adjust the nitrogen supply.

In the second mode, when it is detected that the output current of the power generation unit 2 is greater than the threshold value, it indicates that there is an excess supply of oxygen in the power generation unit 2. Therefore, it may be necessary to first reduce the supply of oxygen until the output current of the power generation unit 2 may be restored to the threshold value. However, if at the same time, the total pressure in the cathode circulation system 2 still remains greater than the preset cathode gas pressure, it indicates that there is also an excess supply of nitrogen, so it may be necessary to reduce the supply of nitrogen.

In the third mode, when the detected output current of the power generation unit 2 is greater than the threshold, it indicates that there is an excess supply of oxygen in the power generation unit 2. Therefore, the oxygen supply must be reduced first until the output current of the power generation unit 2 may return to the threshold. However, if at the same time, the total pressure in the cathode circulation system 2 still exhibits a value less than the preset cathode gas pressure, it indicates that there is a leakage of nitrogen gas. Therefore, the nitrogen supply must be increased.

To summarize the above sections, if FO1 represents the oxygen supply flow rate, FO2 represents the actual oxygen consumption, FO3 represents the oxygen leakage, FN1 represents the nitrogen supply, FN2 represents the nitrogen leakage, and FO3′ represents the oxygen gain, these parameters satisfy the following formula (1):

FO1+FN1=FO2+FO3+FN2  (Formula 1)

Expressed in terms of gain, the following formula (2) may be satisfied:

FO1=FO2+FO3′  (Formula 2)

Therefore, the cathode gas pump 16 may provide the corresponding gain value based on the above calculations.

Although the output current of the power generation unit 2 is used as an example in the above, in fact, the concentration of the reaction gas may also be detected as the criterion for judgment. In addition, parameters such as output current, concentration of reaction gas, and cathode gas pressure will vary depending on the design of different fuel cells and differences in oxygen concentration in the reaction gas.

Furthermore, please refer to FIGS. 2A and 2B, which show another embodiment of the disclosure. FIG. 2A illustrates a block diagram of the cathode circulation system of the fuel cell of the disclosure, and FIG. 2B illustrates a corresponding flowchart of the control method for the cathode circulation system in FIG. 2A.

In the present embodiment, the cathode circulation system 1, connected to the power generation unit 2 of the fuel cell, includes at least two gas supply tanks 11 a, 11 b, a mixing tank 12, a humidifier 13, a gas-water separator 14, a buffer tank 15, and at least one cathode gas pump 16, as disclosed in the disclosure. Each of the gas supply tanks 11 a, 11 b provides an inert gas and a reactant gas, respectively. The mixing tank 12 is connected to the gas supply tanks 11 a, 11 b and is used to mix the inert gas and the reactant gas. The humidifier 13 is connected between the mixing tank 12 and the power generation unit 2. The gas-water separator 14 is connected to the power generation unit 2. The buffer tank 15 is connected between the gas-water separator 14 and the mixing tank 12. In contrast to FIGS. 1A and 1B, the cathode gas pump 16 is connected between the buffer tank 15 and the mixing tank 12, as illustrated in FIGS. 2A and 2B.

Therefore, in the control process shown in FIG. 2B, first, in step S01 a, nitrogen (an inert gas) is supplied to the cathode circulation system 1 from the supply gas tanks 11 a and 11 b; then, when the pressure of nitrogen in the mixing tank 12 is not greater than 80% of the operating pressure value, oxygen (a reaction gas) is supplied to the cathode circulation system 1, as shown in step S02 a; next, in step S03 a, oxygen is continuously supplied to the mixing tank 12 until the pressure value in the mixing tank 12 reaches the set operating pressure value. After the mixed nitrogen and oxygen are humidified by the humidifier 13, they are conveyed to the power generation unit 2 to undergo the redox reaction. Finally, in step S04 a, the actual oxygen consumption is calculated based on the output current of the power generation unit 2, and the settings of the flow meters 17 a and 17 b are adjusted accordingly. At the same time, the cathode gas pump 16 provides a gain value to adjust the gas flowing through the mixing tank 12. The unreacted gas may be recovered and returned to the supply pipeline before being recycled by passing through the gas-water separator 14 and the buffer tank 15. The recovered gas may be stabilized and returned to the mixing tank 12 through the cathode gas pump 16.

Compared to the configuration shown in FIGS. 1A and 1B, this design results in less gas flow through the cathode gas pump 16 and therefore lower energy consumption by the cathode gas pump 16 itself.

While this embodiment has a different pipeline layout from the previous embodiment described the logic for controlling the supply of oxygen and nitrogen is the same as the previous embodiment, and therefore will not be further elaborated here.

As described above, the cathode circulation system and control method of the fuel cell disclosed in the disclosure may monitor the output current of the fuel cell and dynamically adjust the supply of oxygen to maintain the efficiency of the redox reaction by calculating the consumption of oxygen based on the output current of the fuel cell. Therefore, it is possible to provide a fuel cell system that uses pure oxygen input without significantly modifying the design of the fuel cell system or increasing the use of proton exchange membranes and catalysts, expanding the application field of the fuel cell while still maintaining excellent energy conversion efficiency and good operational safety.

The presently disclosed inventive concepts are not intended to be limited to the embodiments shown herein, but are to be accorded their full scope consistent with the principles underlying the disclosed concepts herein. Directions and references to an element, such as “up,” “down,”, “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” and the like, do not imply absolute relationships, positions, and/or orientations. Terms of an element, such as “first” and “second” are not literal, but, distinguishing terms. As used herein, terms “comprises” or “comprising” encompass the notions of “including” and “having” and specify the presence of elements, operations, and/or groups or combinations thereof and do not imply preclusion of the presence or addition of one or more other elements, operations and/or groups or combinations thereof. Sequence of operations do not imply absoluteness unless specifically so stated. Reference to an element in the singular, such as by use of the article “a” or “an”, is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. As used herein, “and/or” means “and” or “or”, as well as “and” and “or.” As used herein, ranges and subranges mean all ranges including whole and/or fractional values therein and language which defines or modifies ranges and subranges, such as “at least,” “greater than,” “less than,” “no more than,” and the like, mean subranges and/or an upper or lower limit. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the relevant art are intended to be encompassed by the features described and claimed herein. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure may ultimately explicitly be recited in the claims. No element or concept disclosed herein or hereafter presented shall be construed under the provisions of 35 USC 112(f) unless the element or concept is expressly recited using the phrase “means for” or “step for”.

In view of the many possible embodiments to which the disclosed principles may be applied, we reserve the right to claim any and all combinations of features and acts described herein, including the right to claim all that comes within the scope and spirit of the foregoing description, as well as the combinations recited, literally and equivalently, in the following claims and any claims presented anytime throughout prosecution of this application or any application claiming benefit of or priority from this application

Various embodiments of the disclosure may have one or more of the following effects. In some embodiments, in view of the bottleneck encountered by the prior art technologies, the present disclosure may provide a cathode circulation system and its control method for a fuel cell. The system may use the proton exchange membrane and catalyst system of a conventional air fuel cell. By improving the cathode circulation system of the fuel cell, nitrogen and oxygen may be mixed and the oxygen concentration may be controlled to be close to the concentration of air before being supplied to the fuel cell reaction. In other embodiments, the purpose of the disclosure may be to provide a cathode circulation system and control method for a fuel cell, which may utilize the conventional proton exchange membrane and catalyst system in an air fuel cell. By improving the fuel cell cathode circulation system, nitrogen and oxygen are mixed, and the oxygen concentration may be controlled to be close to the concentration of air before supplying it to the fuel cell reaction. In further embodiments, the purpose of the disclosure may be to provide a cathode circulation system and its control method for a fuel cell, which may monitor at least one of the output current of the fuel cell and the concentration of reaction gas, and may adjust the supply of oxygen by calculating the consumption of oxygen based on the output current of the fuel cell.

In some embodiments, an advantage of the disclosure may be that by improving the cathode circulation system of a conventional air fuel cell, the nitrogen gas may be mixed with the oxygen gas, and the oxygen concentration may be controlled to be close to the concentration of air before being supplied to the fuel cell reaction, while still using the proton exchange membrane and catalyst system inside the air fuel cell.

In other embodiments, the efficacy of the disclosure lies in the improvement of the cathode circulation system of a conventional air fuel cell that uses a proton exchange membrane and a catalyst system. By mixing nitrogen and oxygen and controlling the oxygen concentration to be close to that of air, the mixed gas is supplied to the fuel cell reaction. This invention may provide a pure oxygen input fuel cell system without significant changes to the fuel cell system design or increasing the amount of proton exchange membrane and catalyst used. This may expand the application field of the fuel cell system while maintaining excellent energy conversion efficiency and good operational safety.

In further embodiments, the disclosure may provide a cathode circulation system of fuel cell and its control method. In the cathode circulation system, the oxygen consumption may be calculated by monitoring at least one of the output current and the concentration of the reaction gas of the fuel cell. By improving the cathode circulation system of the fuel cell to control the concentration of oxygen, the proton exchange membrane and catalyst system of a conventional air fuel cell may be directly used in a fuel cell system that supplies pure oxygen gas.

Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present disclosure. Embodiments of the present disclosure have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present disclosure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. Unless indicated otherwise, not all steps listed in the various figures need be carried out in the specific order described. 

The disclosure claimed is:
 1. A cathode circulation system of a fuel cell connected to a power generation unit of the fuel cell, the cathode circulation system comprises: a first gas supply tank for providing an inert gas; a second gas supply tank for providing a reaction gas; a mixing tank connected to the first gas supply tank and the second gas supply tank for mixing the inert gas and the reaction gas; a gas-liquid separator connected to the power generation unit; and at least one cathode gas pump provided between the mixing tank and the gas-liquid separator and between the mixing tank and the power generation unit.
 2. The cathode circulation system of claim 1, wherein a humidifier is provided between the mixing tank and the power generation unit.
 3. The cathode circulation system of claim 1, wherein a buffer tank is provided between the gas-liquid separator and the mixing tank.
 4. The cathode circulation system of claim 1, wherein: a first flow meter is provided between the first gas supply tank and the mixing tank; and a second flow meter is provided between the second gas supply tank and the mixing tank.
 5. The cathode circulation system of claim 4, wherein each one of the first flow meter and the second flow meter operates individually or simultaneously based on at least one of a concentration gradient and a pressure gradient of at least one of the inert gas and the reaction gas in the cathode circulation system.
 6. The cathode circulation system of claim 4, wherein the at least one cathode gas pump provides a gain value based on an operation of at least one of the first flow meter and the second flow meter.
 7. The cathode circulation system of claim 1, wherein: the at least one cathode gas pump is provided between the mixing tank and a buffer tank; and a valve or a pump is provided between the mixing tank and a humidifier, which may be same or different from the at least one cathode gas pump.
 8. The cathode circulation system of claim 1, wherein: a reaction gas concentration meter is provided between the mixing tank and the power generation unit; and the reaction gas concentration meter is set with a system operation concentration threshold.
 9. The cathode circulation system of claim 1, wherein a temporary water tank is provided between the gas-liquid separator and a buffer tank.
 10. The cathode circulation system of claim 1, wherein a mixing ratio of the reaction gas and the inert gas is substantially similar to that of oxygen and nitrogen in air.
 11. A method for controlling the cathode circulation system of claim 1, comprising following steps: providing the inert gas to the cathode circulation system; providing the reaction gas to the cathode circulation system when a pressure value of the inert gas in the mixing tank is not greater than 80% of an operating pressure value; delivering mixture of the inert gas and the reaction gas to the power generation unit for redox reactions until the pressure value in the mixing tank reaches the operating pressure value; and detecting at least one of an output current of the power generation unit and a concentration of the reaction gas and adjusting a flow rate of at least one of the inert gas and the reaction gas.
 12. The method for controlling the cathode circulation system of claim 11, wherein, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is less than a corresponding threshold value, further increasing a supply of the reaction gas and selectively adjusting a supply of the inert gas, wherein a threshold value for the output current corresponds to a current value and another threshold value for the concentration of the reaction gas corresponds to a concentration value.
 13. The method for controlling the cathode circulation system of claim 12, wherein, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is less than the corresponding threshold value and a total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing the supply of the reaction gas, and as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value but the total pressure in the cathode circulation system is still less than the set cathode gas pressure, further increasing the supply of the inert gas until the total pressure in the cathode circulation system is equal to the set cathode gas pressure.
 14. The method for controlling the cathode circulation system of claim 12, wherein, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is less than the corresponding threshold value and a total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing the supply of the reaction gas, and as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value and the total pressure in the cathode circulation system is equal to the set cathode gas pressure, further making no adjustment for the inert gas.
 15. The method for controlling the cathode circulation system of claim 11, wherein, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to a corresponding threshold value and a total pressure in the cathode circulation system is less than a set cathode gas pressure, further increasing a supply of the inert gas but making no adjustment for the reaction gas, and stopping supplying the inert gas until the total pressure in the cathode circulation system is equal to the set cathode gas pressure, wherein the threshold value for the output current corresponds to a current value and the threshold value for the concentration of the reaction gas corresponds to a concentration value.
 16. The method for controlling the cathode circulation system of claim 11, wherein, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is larger than a corresponding threshold value, further reducing a supply of the reaction gas until at least one of the output current and the concentration of the reaction gas is equal to the corresponding threshold value, and a total pressure in the cathode circulation system is equal to a set cathode gas pressure, wherein the threshold value for the output current corresponds to a current value and the threshold value for the concentration of the reaction gas corresponds to a concentration value.
 17. The method for controlling the cathode circulation system of claim 16, wherein, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is larger than the corresponding threshold value, further reducing a supply of the reaction gas, and further reducing the supply of the inert gas until as at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value, but the total pressure in the cathode circulation system is larger than the set cathode gas pressure.
 18. The method for controlling the cathode circulation system of claim 16, wherein, in the step of detecting at least one of the output current of the power generation unit and the concentration of the reaction gas, as at least one of the output current of the power generation unit and the concentration of the reaction gas is larger than the corresponding threshold value, further reducing a supply of the reaction gas, and further increasing the supply of the inert gas until at least one of the output current of the power generation unit and the concentration of the reaction gas is equal to the corresponding threshold value, but the total pressure in the cathode circulation system is less than the set cathode gas pressure.
 19. The method for controlling the cathode circulation system of claim 11, further comprising changing a gain of the cathode gas pump for adjusting when adjusting the flow rate of at least one of the inert gas and the reaction gas. 